chan_alloc: Change Channel Release to release SAPIs, then the channel
Currently every SAPI release indication will trigger the channel. It
was possible that we had SAPI=3 and SAPI=0 allocated and we tried to
release the channel by sending a RF Channel Release, the BTS answered
with a RF Channel Release ACK but also sent the SAPI Release Indication
which triggered a channel release here. So it was possible that we
would have released a newly allocated channel because of the SAPI
release of the old connection.
This code now works by releasing all SAPIs from highest to lowest,
then sending a SACH Deactivate and finally releasing the channel. This
approach is in use on the on-waves/bsc-master.
diff --git a/openbsc/src/chan_alloc.c b/openbsc/src/chan_alloc.c
index b061fc7..5325dc0 100644
--- a/openbsc/src/chan_alloc.c
+++ b/openbsc/src/chan_alloc.c
@@ -328,6 +328,9 @@
lchan->conn = NULL;
}
+ lchan->sach_deact = 0;
+ lchan->release_reason = 0;
+
/* FIXME: ts_free() the timeslot, if we're the last logical
* channel using it */
}
@@ -352,18 +355,62 @@
lchan->state = LCHAN_S_NONE;
}
+/* release the next allocated SAPI or return 0 */
+static int _lchan_release_next_sapi(struct gsm_lchan *lchan)
+{
+ int sapi;
+
+ for (sapi = 1; sapi < ARRAY_SIZE(lchan->sapis); ++sapi) {
+ u_int8_t link_id;
+ if (lchan->sapis[sapi] == LCHAN_SAPI_UNUSED)
+ continue;
+
+ link_id = sapi;
+ if (lchan->type == GSM_LCHAN_TCH_F || lchan->type == GSM_LCHAN_TCH_H)
+ link_id |= 0x40;
+ rsl_release_request(lchan, link_id, lchan->release_reason);
+ return 0;
+ }
+
+ return 1;
+}
+
+/* Drive the release process of the lchan */
+static void _lchan_handle_release(struct gsm_lchan *lchan)
+{
+ /* Ask for SAPI != 0 to be freed first and stop if we need to wait */
+ if (_lchan_release_next_sapi(lchan) == 0)
+ return;
+
+ if (lchan->sach_deact) {
+ gsm48_send_rr_release(lchan);
+ return;
+ }
+
+ rsl_release_request(lchan, 0, lchan->release_reason);
+ rsl_lchan_set_state(lchan, LCHAN_S_REL_REQ);
+}
+
+/* called from abis rsl */
+int rsl_lchan_rll_release(struct gsm_lchan *lchan, u_int8_t link_id)
+{
+ if (lchan->state != LCHAN_S_REL_REQ)
+ return -1;
+
+ if ((link_id & 0x7) != 0)
+ _lchan_handle_release(lchan);
+ return 0;
+}
/* Consider releasing the channel now */
int lchan_release(struct gsm_lchan *lchan, int sach_deact, int reason)
{
- /* Assume we have GSM04.08 running and send a release */
- if (sach_deact) {
- gsm48_send_rr_release(lchan);
- }
-
- DEBUGP(DRLL, "%s Recycling Channel\n", gsm_lchan_name(lchan));
+ DEBUGP(DRLL, "%s starting release sequence\n", gsm_lchan_name(lchan));
rsl_lchan_set_state(lchan, LCHAN_S_REL_REQ);
- rsl_release_request(lchan, 0, 0);
+
+ lchan->release_reason = reason;
+ lchan->sach_deact = sach_deact;
+ _lchan_handle_release(lchan);
return 1;
}